If I could change one thing it would be all the bullying that is going on in the world.  There is so much hate, violence, negativity, and just plain stupidity.  They do not seem to realize that their words and actions could hurt people around them.  I would put the best effort I have into changing this.  I would stop the words and actions before they even have a chance to surface.  I as a teenage girl know how it feels to be bullied and tormented by those who feel a need to hate on the people that are different and that might be just not quite the same as everyone else.  If I had the chance I would put the world on hold to show them all the pain bullying can cause.